1. Field of the Invention
The present invention relates to motor control apparatuses for driving motors, such as stepper motors, by switching the excitation phase thereof, and more particularly, to a motor control apparatus having a plurality of operation modes, such as a ramping up/down mode (acceleration driving/deceleration driving), a constant-speed driving mode, and a holding operation mode.
2. Description of the Related Art
A constant-voltage driving method and a constant-current driving method are generally employed for driving stepper motors. The constant-voltage driving method is widely used because the circuit implementing this method has a simple structure and is inexpensive. When the rotation frequency of a motor becomes high, however, the current of a motor winding has a long rising time due to the inductance of the motor winding. Therefore, motor torque is reduced at high-speed rotation to make high-speed rotation impossible.
In the constant-current driving method, the voltage to be applied and the winding inductance are set so as to make the time constant of the motor winding small and the current flowing through the winding is kept constant by switching on and off the current by the use of a switching device, such as a transistor, while the current is being detected, such that the current matches the detected current. When the constant-current driving method is employed, high-speed motor rotation can be performed although the circuit implementing this method has a complicated structure and is expensive. A constant-current driving circuit has been integrated into an IC these days, and therefore, constant-current driving is allowed at a low cost.
When high-speed driving is applied to a stepper motor with the above-described condition, rotation control is generally achieved in control zones, such as an acceleration zone where the motor is accelerated to a target rotation speed, a constant-speed zone where the target rotation speed is maintained, and a deceleration zone where the motor is decelerated and stopped. In the acceleration zone and the deceleration zone, it is necessary to set the rotation torque of the motor higher than in the constant-speed zone in order to change the rotation speed within a relatively short period of time. A method for changing the driving current in the acceleration zone, the constant-speed zone, and the deceleration zone is used.
FIG. 9 and FIG. 10 are views showing the relationship between the target current and the motor winding current in a conventional constant-current driving method. FIG. 9 shows the relationship obtained near the start of the acceleration zone, and FIG. 10 shows the relationship obtained near the end of the deceleration zone. In each figure, the upper part indicates the relationship in phase A of the motor and the lower part indicates the relationship in phase B. A solid line illustrates the target current in each part, and a dotted line illustrates the motor winding current in each part. The maximum winding-current values required to obtain necessary rotation torque in the acceleration zone in the phases are indicated by +IA1, xe2x88x92IA1, +IB1, and xe2x88x92IB1, and the maximum winding-current values required to obtain necessary rotation torque in the deceleration zone in the phases are indicated by +IA2, xe2x88x92IA2, +IB2, and xe2x88x92IB2.
It is understood from FIG. 9 that the rotation frequency increases in the direction from the left to the right in the figure as an acceleration operation is achieved, the winding current flows more than necessary against the target current near the start of acceleration, and the winding current approaches the maximum target winding current as the rotation frequency increases. It is also understood from FIG. 10 that the rotation frequency is reduced in the direction from the left to the right as a deceleration operation is achieved, the winding current is close to the maximum target winding current near the start of deceleration, and the winding current flows more than necessary as the rotation frequency is reduced.
Ideal control can be achieved so that the winding current always matches the target current, by improving the switching characteristic of a driving circuit and by reducing the winding resistance and inductance to improve the response of the current flowing through the winding. To rotate the motor at a high speed, expensive components are required, and the cost of the motor control apparatus increases.
Therefore, as shown in FIG. 9 and FIG. 10, the maximum target current is specified for the motor winding current such that an appropriate rotation torque is generated at a high-rotation-frequency area if high rotation torque is required at acceleration and deceleration. Since the winding current flows more than necessary near the start of acceleration and near the end of deceleration in this method, however, a large-capacity power supply having a large maximum rating is used to drive the motor with the maximum supply current being taken into account. This type of power supply is expensive.
In addition, since the winding current flows more than necessary near the start of acceleration and near the end of deceleration, wasteful motor heat is generated and motor vibration occurs due to wasteful applied rotation torque, and noise also occurs.
Accordingly, it is an object of the present invention to provide a motor control apparatus for preventing a motor-winding current from flowing more than necessary to allow stable motor rotation.
Another object of the present invention is to suppress the driving current of a stepper motor near the start of an acceleration mode and near the end of a deceleration mode to allow the stepper motor to be rotated at high speed with low cost.
According to one aspect, the present invention that achieves at least one of the foregoing objects relates to a motor control apparatus comprising a stepper motor, driving means, excitation-signal generation means, a timer, pulse generation means, storage means, and control means. The driving means is for driving the stepper motor. The excitation-signal generation means is for applying an excitation signal to the driving means to drive the stepper motor when the excitation signal is switched. The timer is for measuring a predetermined period of time at the end of which the excitation signal is switched. The pulse generation means is for applying a pulse signal having a specified duty cycle to the driving means to control the driving current of the stepper motor. The storage means is for storing motor-control-table information for various driving modes of the stepper motor including at least an acceleration mode and a deceleration mode. The control means is for specifying for the pulse generation means information required for generating a pulse signal having a duty cycle specified according to the motor control-table information of a driving mode. The information includes information used by the driving means to suppress the driving current of the stepper motor near the start of the acceleration mode and near the end of the deceleration mode. The control means is also for controlling the timer to start measuring the predetermined period of time and for controlling the excitation signal generation means to switch the excitation signal at the end of the measured predetermined period of time.
Among the driving modes for which the motor control-table information is stored in the storage means, the acceleration mode has a current-suppression table for acceleration and a normal table for acceleration, and the deceleration mode has a current-suppression table for deceleration and a normal table for deceleration. The control means makes the timer start measuring the predetermined period of time and controls the driving means to drive the stepping motor according to the various driving modes for which the motor control-table information is stored in the storage means, according to the time measured by the timer. The control means controls the driving means to drive the stepping motor according to the driving modes in synchronization with the timing when the excitation signal is switched.
According to another aspect, the present invention that achieves at least one of these objects, relates to a motor control apparatus comprising a stepper motor, driving means, excitation-signal generation means, pulse generation means, storage means, and control means. The driving means is for driving the stepper motor with a driving current. The excitation-signal generation means is for applying an excitation signal to the driving means to drive the stepper motor when the excitation signal is switched. The pulse generation means is for applying a pulse signal having a specified duty cycle to the driving means to control the driving current of the stepper motor. The storage means is for storing motor-control-table information for various driving modes of the stepper motor including at least an acceleration mode, a constant-speed mode, and a deceleration mode. The control means is for specifying for the pulse generation means information required for generating a pulse signal having a duty cycle specified according to the motor control-table information of a driving mode. The information includes information used by the driving means for suppressing the driving current of the stepper motor near the start of the acceleration mode and near the end of the deceleration mode. The control means is also for controlling the excitation-signal generation means to switch the excitation signal.
The stepper motor comprises means for providing a driving source of a carriage control mechanism of a printer. The stepper motor also comprises means for providing high-speed printing for the carriage control mechanism.
According to another aspect, the present invention that achieves at least one of these objects, relates to a motor control apparatus comprising a motor, driving means, excitation-signal generation means, specifying means, storage means, and control means. The driving means is for driving the motor with a driving current. The excitation-signal generation means is for applying an excitation signal to the driving means to drive the motor when the excitation signal is switched. The specifying means is for specifying the driving current supplied to the motor by the driving means. The storage means is for storing motor-control-table information for various driving modes of the motor including at least an acceleration mode and a deceleration mode. The control means is for controlling the specifying means to specify the driving current according to the motor-control-table information of a driving mode, for specifying information used by the driving means for suppressing the driving current of the motor near the start of the acceleration mode and near the end of the deceleration mode, and for controlling the excitation-signal generation means to switch the excitation signal.
According to another aspect, the present invention that achieves at least one of these objects, relates to a motor control apparatus comprising a stepper motor, driving means, excitation-signal generation means, specifying means, storage means, and control means. The driving means is for driving the stepper motor with a driving current. The excitation-signal generation means is for applying an excitation signal to the driving means to drive the stepper motor when the excitation signal is switched. The specifying means is for specifying the driving current supplied to the motor by the driving means. The storage means is for storing motor-control-table information in a motor control table for various driving modes of the stepper motor including at least an acceleration mode and a deceleration mode. The control means is for controlling the specifying means to specify means the driving current according to the motor-control-table information of a driving mode, and for controlling the excitation-signal generation means to switch the excitation signal. The motor control table includes information used by the control means to control the specifying means to specify a driving current corresponding to at least N microsteps within one step driving of the stepper motor, where N is a positive integer. The motor control table includes a current-suppression table for acceleration in the acceleration mode and a normal table for acceleration in the acceleration mode. The motor control table includes a current-suppression table for deceleration in the deceleration mode and a normal table for deceleration in the deceleration mode. The control means controls the specifying means to specify the driving current according to the current-suppression table for acceleration at the start of the acceleration mode. The control means switches the motor control table used for controlling the specifying means after counting the number of microsteps during acceleration. The control means controls the specifying means to specify the driving current according to the normal table for acceleration. The control means controls the specifying means to specify the driving current according to the normal table for deceleration at the start of the deceleration mode. The control means switches the motor control table used for controlling the specifying means after counting the number of microsteps during deceleration. The control means controls the specifying means to specify the driving current according to the current suppression table for deceleration.
According to still another aspect, the present invention that achieves at least one of these objects, relates to a motor control apparatus comprising a stepper motor, driving means, specifying means, and control means. The stepper motor is capable of operating in an acceleration mode and a deceleration mode. The driving means is for driving the stepper motor with a driving current. The excitation-signal generation means is for applying an excitation signal to the driving means to drive the stepper motor when the excitation signal is switched. The specifying means is for specifying the driving current supplied to the stepper motor by the driving means. The control means is for controlling the specifying means to specify the driving current according to a driving mode of the stepper motor, and for controlling the excitation-signal generation means to switch the excitation signal. The control means controls the specifying means so as to suppress the driving current of the stepper motor near the start of an acceleration mode and near the end of a deceleration mode.
According to still another aspect, the present invention that achieves at least one of these objects relates to a motor control apparatus for outputting an excitation signal to a stepper motor to drive the stepper motor in driving modes including an acceleration mode and a deceleration mode. The apparatus comprises means for specifying a driving current of the stepper motor according to each driving mode, determination means for determining the driving mode of the stepper motor, and means for suppressing the driving current near the start of the acceleration mode and near the end of the deceleration mode.
According to still another aspect, the present invention that achieves at least one of these objects relates to a motor control apparatus for outputting an excitation signal of a stepper motor to drive the stepper motor in driving modes including an acceleration mode and a deceleration mode, comprising means for specifying a driving current of the motor according to each driving mode, determination means for determining the driving mode of the stepper motor, and stepper-motor driving means for driving the stepper motor according to a microstep driving method driving the stepper motor in microsteps within one step driving of the stepper motor. The stepper-motor driving means comprises means for specifying the driving current of the stepper motor at least N times within one step driving of the stepper motor, where N is a positive integer. The apparatus further comprises means for counting the number of microsteps of the stepper motor during the acceleration mode from the start of the acceleration mode, and means for counting the number of microsteps of the stepper motor during the deceleration mode from the start of the deceleration mode. In addition, the apparatus also comprises means for achieving driving of the stepping motor at a first maximum target driving current or less at the start of the acceleration mode, means for switching the driving of the stepping motor to a second maximum target driving current or less after the number of microsteps performed during the acceleration mode reaches a predetermined number, means for achieving driving of the stepping motor at a third maximum target driving current or less at the start of the deceleration mode, and means for switching the driving of the stepping motor to a fourth maximum target driving current or less after the number of microsteps performed during the deceleration mode reaches a predetermined number. The apparatus also comprises timer measuring means for measuring a predetermined period of time at the end of which the driving of the stepper motor is switched, means for selecting motor-driving control information including time information of the predetermined time measured by the timer measuring means and target driving current information for each microstep driving, according to a target driving speed, wherein the motor-driving control information is stored in a memory, and means for sequentially reading the time information from the memory to set it for the timer measuring means and for reading the target driving current information from the memory to achieve motor driving control with the two switching means and the two achieving means using the read target driving current information. The motor-driving control information includes microstep information used in the acceleration mode by the first-maximum-target-driving-current achieving means until the maximum target current is switched by the second-maximum-target-driving-current switching means. The motor-driving control information includes microstep information used in the deceleration mode by the third-maximum-target-driving-current achieving means until the maximum target current is switched by the fourth-maximum-target-current switching means.
According to still another aspect, the present invention that achieves at least one of these objects relates to a motor control apparatus for outputting an excitation signal to a stepper motor to drive the stepper motor in driving modes including an acceleration mode and a deceleration mode. The apparatus comprises means for specifying a driving current of the stepper motor, determination means for determining the driving mode of the stepper motor, first target-current specifying means for specifying a target current corresponding to a motor winding current near the start of the acceleration mode and near the end of the deceleration mode, and second target-current specifying means for specifying a target current more than the motor winding current near the start of the acceleration mode and near the end of the deceleration mode.
According to yet another aspect, the present invention that achieves at least one of these objects relates to a motor control apparatus comprising a stepper motor, a motor driving circuit, an excitation-signal generation circuit, a timer circuit, a pulse modulator unit, a memory, and a processor. The motor driving circuit is connected to the stepper motor and drives the stepper motor. The excitation-signal generation circuit is connected to the motor driving circuit and applies an excitation signal to the motor driving circuit to drive the stepper motor when the excitation signal is switched. The timer circuit is connected to the excitation signal generation circuit and measures a predetermined period of time at the end of which the excitation signal is switched. The pulse modulator unit is connected to the motor driving circuit and applies a pulse signal having a specified duty cycle to the motor driving circuit control the driving current of the stepper motor. The memory stores motor-control-table information for various driving modes of the stepper motor including at lease an acceleration mode and a deceleration mode. The processor is connected to the memory, the pulse modulator circuit, the timer circuit, and the excitation-signal generation circuit. The processor specifies the pulse modulator unit information required for generating a pulse signal having a duty cycle specified according to the motor control-table information of a driving mode. The information includes information used by the motor driving circuit to suppress the driving current of the stepper motor near the start of the acceleration mode and near the end of the deceleration mode. The processor controls the timer to start measuring the predetermined period of time. The processor controls the excitation-signal generation circuit to switch the excitation signal at the end of the measured predetermined period of time.
Among the driving modes for which the motor control-table information is stored in the memory, the acceleration mode has a current-suppression table for acceleration and a normal table for acceleration, and the deceleration mode has a current-suppression table for deceleration and a normal table for deceleration. In addition, the processor makes the timer circuit start measuring the predetermined period of time and controls the motor driving circuit to drive the stepping motor according to the various driving modes for which the motor control-table information is stored in the memory, according to the time measured by the timer circuit. The processor controls the motor driving circuit to drive the stepping motor according to the driving modes in synchronization with the timing when the excitation signal is switched.
According to yet another aspect, the present invention that achieves at least one of these objects relates to a motor control apparatus comprising a motor driving circuit, an excitation-signal generation circuit, a pulse modulator unit, a memory, and a processor. The motor driving circuit is connected to the stepper motor and drives the stepper motor with a driving current. The excitation-signal generation circuit is connected to the motor driving circuit and applies an excitation signal to the motor driving circuit to drive the stepper motor when the excitation signal is switched. The pulse modulator unit is connected to the motor driving circuit and applies a pulse signal having a specified duty cycle to the motor driving circuit to control the driving current of the stepper motor. The memory stores motor-control-table information for various driving modes of the stepper motor including at least an acceleration mode, a constant-speed mode, and a deceleration mode. The processor is connected to the memory, the pulse modulator unit, and excitation-signal generation unit, and the motor driving unit. The processor specifies for the pulse modulator unit information required for generating a pulse signal having a duty cycle specified according to the motor control-table information of a driving mode. The information includes information used by the motor driving circuit for suppressing the driving current of the stepper motor near the start of the acceleration mode and near the end of the deceleration mode. The processor controls the excitation-signal generation circuit to switch the excitation signal. The stepper motor provides a driving source of a carriage control mechanism of a printer. In addition, the stepper motor provides high-speed printing for the carriage control mechanism.
According to yet another aspect, the present invention that achieves at least one of these objects relates to a motor control apparatus comprising a motor, a motor driving circuit connected to the motor and driving the motor with a driving current, an excitation-signal generation circuit connected to the motor driving circuit and applying an excitation signal to the motor driving circuit to drive the motor when the excitation signal is switched, a modulator unit connected to the motor driving circuit and specifying the driving current supplied to the motor by the motor driving circuit, a memory storing motor-control-table information for various driving modes of the motor including at least an acceleration mode and a deceleration mode, and a processor connected to the memory, the modulator unit, the excitation-signal generation circuit, and the motor driving circuit and controlling the modulator unit to specify the driving current according to the motor-control-table information of a driving mode. The processor specifies information used by the motor driving circuit for suppressing the driving current of the motor near the start of the acceleration mode and near the end of the deceleration mode. The processor controls the excitation-signal generation circuit to switch the excitation signal.
According to yet another aspect, the present invention that achieves at least one of these objects relates to a motor control apparatus comprising a stepper motor, a motor driving circuit connected to the stepper motor and driving the stepper motor with a driving current, an excitation-signal generation circuit connected to the motor driving circuit and applying an excitation signal to the motor driving circuit to drive the stepper motor when the excitation signal is switched, a modulator unit connected to the motor driving circuit and specifying the driving current supplied to the motor by the motor driving circuit, a memory storing motor-control-table information in a motor control table for various driving modes of the stepper motor including at least an acceleration mode and a deceleration mode, and a processor connected to the memory, the modulator unit, the excitation-signal generation circuit, and the motor driving circuit and controlling the modulator unit to specify the driving current according to the motor-control-table information of a driving mode. The processor controls the excitation-signal generation circuit to switch the excitation signal. The motor control table includes information used by the processor to control the modulator unit to specify a driving current corresponding to at least N microsteps within one step driving of the stepper motor, wherein N is a positive integer. The motor control table includes a current-suppression table for acceleration in the acceleration mode and a normal table for acceleration in the acceleration mode. The motor control table includes a current-suppression table for deceleration in the deceleration mode and a normal table for deceleration in the deceleration mode. The processor controls the modulator unit to specify the driving current according to the current-suppression table for acceleration at the start of the acceleration mode. The processor switches the motor control table used for controlling the modulator unit after counting the number of microsteps during acceleration. The processor controls the modulator unit to specify the driving current according to the normal table for acceleration. The processor controls the modulator unit to specify the driving current according to the normal table for deceleration at the start of the deceleration mode. The processor switches the motor control table used for controlling the modulator nit after counting the number of microsteps during deceleration. The controller controls the modulator unit to specify the driving current according to the current suppression table for deceleration.
According to yet another aspect, the present invention that achieves at least one of these objects relates to a motor control apparatus comprising a stepper motor capable of operating in an acceleration mode and a deceleration mode, a motor driving circuit connected to the stepper motor and driving the stepper motor with a driving current, an excitation-signal generation circuit connected to the motor driving circuit and applying an excitation signal to the motor driving circuit to drive the stepper motor when the excitation signal is switched, a modulator unit connected to the motor driving circuit and specifying the driving current supplied to the stepper motor by the motor driving circuit, and a processor connected to the modulator unit, the excitation-signal generation circuit, and the motor driving circuit and controlling the modulator unit to specify the driving current according to a driving mode of the stepper motor. The processor controls the excitation-signal generation unit to switch the excitation signal. The processor controls the modulator unit so as to suppress the driving current of the stepper motor near the start of an acceleration mode and near the end of a deceleration mode.
According to yet another aspect, the present invention that achieves at least one of these objects relates to a motor control apparatus for outputting an excitation signal to a stepper motor to drive the stepper motor in driving modes including an acceleration mode and a deceleration mode. The apparatus comprises a modulator unit connected to the stepping motor and specifying a driving current of the stepper motor according to each driving mode and a processor, connected to the modulator unit and to the stepping motor. The processor determines the driving mode of the stepper motor. The processor controls the modulator unit to suppress the driving current near the start of the acceleration mode and the near the end of the deceleration mode.
According to yet another aspect, the present invention that achieves at least one of these objects relates to a motor control apparatus for outputting an excitation signal of a stepper motor to drive the stepper motor in driving modes including an acceleration mode and a deceleration mode. The apparatus comprises a modulator unit connected to the stepper motor and specifying a driving current of the motor according to each driving mode, a processor connected to the modulator unit and to the stepping motor and determining the driving mode of the stepper motor, and a stepper-motor driving circuit connected to the processor and driving the stepper motor according to a microstep driving method driving the stepper motor in microsteps within one step driving of the stepper motor. The stepper-motor driving circuit specifies the driving current of the stepper motor at least N times within one step driving of the stepper motor, wherein N is a positive integer. The processor counts the number of microsteps of the stepper motor during the acceleration mode from the start of the acceleration mode. The processor counts the number of microsteps of the stepper motor during the deceleration mode from the start of the deceleration mode. The processor controls the modulator unit to cause the modulator unit to achieve driving of the stepping motor at a first maximum target driving current or less at the start of the acceleration mode. The processor controls the modulator unit to switch the driving of the stepping motor to a second maximum target driving current or less after the number of microsteps performed during the acceleration mode reaches a predetermined number. The processor controls the modulator unit to cause the modulator unit to achieve driving of the stepping motor at a third maximum target driving current or less at the start of the deceleration mode. The processor controls the modulator unit to switch the driving of the stepping motor to a fourth maximum target driving current or less after the number of microsteps performed during the deceleration mode reaches a predetermined number. The apparatus also comprises a timer circuit connected to the processor and measuring a predetermined period of time at the end of which the driving of the stepper motor is switched. The processor selecting motor-driving control information including time information of the predetermined time measured by the timer circuit and target driving current information for each microstep driving, according to a target driving speed, wherein the motor-driving control information is stored in a memory. The processor sequentially reads the time information from the memory to set it for the timer circuit and reading the target driving current information from the memory to achieve motor driving control with the modulator unit using the read target driving current information. The motor-driving control information includes microstep information used in the acceleration mode by the processor to achieve the first maximum target driving current until the maximum target current is switched to the second maximum target driving current by the processor. The motor-driving control information includes microstep information used in the deceleration mode by the processor to achieve the third maximum target driving current until the maximum target current is switched to the fourth maximum target driving current by the processor.
According to yet another aspect, the present invention that achieves at least one of these objects relates to a motor control apparatus for outputting an excitation signal to a stepper motor to drive the stepper motor in driving modes including an acceleration mode and a deceleration mode. The apparatus comprises a processor, connected to the stepping motor and specifying a driving current of the stepper motor. The processor determines the driving mode of the stepper motor. The processor specifies a target current corresponding to a motor winding current near the start of the acceleration mode and near the end of the deceleration mode. The processor specifies a target current more than the motor winding current near the start of the acceleration mode and near the end of the deceleration mode.
According to yet another aspect, the present invention that achieves at least one of these objects relates to a method of controlling a stepper motor to be driven in an acceleration mode and a deceleration mode comprising the steps of specifying the duty cycle of a pulse signal suppressing the driving current of the stepper motor near the start of the acceleration mode or the end of the deceleration mode in accordance with stored motor control table information, measuring a predetermined time from the start of the duty cycle of the pulse signal suppressing the driving current of the stepper motor near the start of the acceleration mode or the end of the deceleration mode in accordance with stored motor control table information, switching an excitation signal at the end of the predetermined period of time measured in the measuring step, and specifying a new duty cycle for a pulse signal to change the driving current of the stepper motor when the excitation signal is switched in the switching step in accordance with stored motor control table information.
The first specifying step specifies the duty cycle of the pulse signal suppressing the driving current of the stepping motor near the start of the acceleration mode in accordance with a stored current-suppression table for acceleration. The first specifying step also specifies the duty cycle of the pulse signal suppressing the driving current of the stepping motor near the end of the deceleration mode in accordance with a stored current-suppression table for deceleration. The second specifying step specifies a new duty cycle of the pulse signal to change the driving current of the stepper motor in the acceleration mode in accordance with a stored normal table for acceleration. The second specifying step also specifies a new duty cycle of the pulse signal to change the driving current of the stepper motor in the deceleration mode in accordance with a stored normal table for deceleration.
The method further comprises the step of controlling a driving circuit to drive the stepper motor with a driving current in accordance with the pulse signal whose duty cycle is specified in the specifying steps and in accordance with the time measured in the measuring step. In addition, the controlling step controls the driving circuit to drive the stepping motor according to the driving modes in synchronization with the timing measured in the measuring step when the excitation signal is switched in the switching step.
According to still another aspect, the present invention that achieves at least one of these objects relates to a method of controlling a stepper motor to be driven in an acceleration mode, a constant-speed mode, and a deceleration mode comprising the steps of specifying the duty cycle of a pulse signal determining the driving current of the stepper motor in the acceleration mode, the constant-speed mode, and the deceleration mode in accordance with stored motor control table information, specifying the duty cycle of a pulse signal suppressing the driving current of the stepper motor near the start of the acceleration mode or the end of the deceleration mode in accordance with stored motor control table information, switching an excitation signal, and specifying a new duty cycle for a pulse signal to change the driving current of the stepper motor when the excitation signal is switched in the switching step in accordance with stored motor control table information. The method further comprises the steps of driving a carriage control mechanism of a printer with the stepper motor and driving the carriage control mechanism to control the printer to perform high-speed printing with the stepper motor.
According to still another aspect, the present invention that achieves at least one of these objects relates to a method of controlling a motor to be driven in at least an acceleration mode and a deceleration mode comprising the steps of specifying the driving current of the motor in the acceleration mode and the deceleration mode in accordance with stored motor control table information, suppressing the driving current of the motor near the start of the acceleration mode or the end of the deceleration mode in accordance with stored motor control table information, switching an excitation signal, and specifying a new driving current of the motor when the excitation signal is switched in the switching step in accordance with stored motor control table information.
According to yet another aspect, the present invention that achieves at least one of these objects relates to a method of controlling a stepper motor to be driven in at least an acceleration mode and a deceleration mode in microsteps within one step. The method comprising the steps of specifying the driving current for the stepper motor according to a stored current-suppression table for acceleration at the start of the acceleration mode, counting the number of microsteps performed by the stepper motor when being driven in the acceleration mode, switching the table used for specifying the driving current from the current-suppression table for acceleration to the normal table for acceleration after the number of counted microsteps reaches a predetermined number during acceleration of the stepping motor in the acceleration mode, specifying the driving current for the stepper motor according to the stored normal table for acceleration in the acceleration mode, specifying the driving current for the stepper motor according to a normal table for deceleration at the start of the deceleration mode, counting the number of microsteps performed by the stepper motor when being driven in the deceleration mode, switching the table used for specifying the driving current from the normal table for deceleration in the deceleration mode to a current-suppression table for deceleration in the deceleration mode after the number of counted microsteps reaches a predetermined number during deceleration of the stepping motor in the deceleration mode, and specifying the driving current for the stepper motor according to the current-suppression table for deceleration at the start of the deceleration mode.
According to yet another aspect, the present invention the achieves at least one of these objects relates to a method of controlling a stepper motor to be driven in at least an acceleration mode and a deceleration mode comprising the steps of specifying the driving current of the motor in accordance with the driving mode in which the stepper motor operates, suppressing the driving current of the motor near the start of the acceleration mode and at the end of the deceleration mode, switching an excitation signal, and specifying a new driving current of the motor when the excitation signal is switched in the switching step after the driving current in the acceleration mode is suppressed in the suppressing step and when the driving current in the deceleration mode is suppressed in the suppressing step.
According to still another aspect, the present invention that achieves at least one of these objects relates to a method of controlling a stepper motor to drive the stepper motor in driving modes including an acceleration mode and a deceleration mode, comprising the steps of determining the driving mode in which the stepping motor will next operate, specifying a driving current of the stepper motor according to the driving mode determined in the determining step, and suppressing the driving current near the start of the acceleration mode and near the end of the deceleration mode.
According to yet another aspect, the present invention that achieves at least one of these objects relates to a method of controlling a stepper motor to drive the stepper motor in driving modes including an acceleration mode and a deceleration mode, comprising the steps of determining the driving mode in which the stepper motor will next operate, specifying a driving current of the stepper motor according to the driving mode determined in the determining step, driving the stepper motor according to a microstep driving method driving the stepper motor in microsteps within one step driving of the stepper motor by specifying the driving current of the stepper motor at least N times within one step driving of the stepper motor, wherein N is a positive integer, counting the number of microsteps of the stepper motor during the acceleration mode from the start of the acceleration mode, counting the number of microsteps of the stepper motor during the deceleration mode from the start o the deceleration mode, driving the stepping motor at a first maximum target driving current or less at the start of the acceleration mode, switching the driving of the stepping motor to a second maximum target driving current or less after the number of microsteps counted in the acceleration mode microstep counting step reaches a predetermined number, driving of the stepping motor at a third maximum target driving current or less at the start of the deceleration mode, and switching the driving of the stepping motor to a fourth maximum target driving current or less after the number of microsteps counted in the deceleration mode microstep counting step reaches a predetermined number.
In addition, the method further comprises the steps of measuring a predetermined period of time at the end of which the driving of the stepper motor is switched in one of the switching steps, selecting motor-driving control information from a memory including time information of the predetermined time to be measured by the measuring step and target driving current information for each microstep driving, according to a target driving speed, and sequentially reading the time information from the memory to set it for the measuring step and for reading the target driving current information from the memory to achieve motor driving control with the two switching and driving steps means using the read target driving current information. The first maximum target driving current driving step achieves the first maximum target driving current by using microstep information of the motor-driving control information in the acceleration mode until the maximum target current is switched in the second-maximum-target-driving-current switching step. The third maximum target driving current driving step achieves the third maximum target driving current by using microstep information of the motor-driving control information in the deceleration mode until the maximum target current is switched in the fourth-maximum-target-driving-current switching step.
According to still another aspect, the present invention that achieves at least one of these objects relates to a method of controlling a stepper motor to drive the stepper-motor in driving modes including an acceleration mode and a deceleration mode, comprising the steps of determining the driving mode in which the stepper motor will next operate, specifying a driving current of the stepper motor in accordance with the driving mode determined in the determining step comprising the steps of specifying a target current corresponding to a motor winding current near the start of the acceleration mode and near the end of the deceleration mode, and specifying a target current more than the motor winding current near the start of the acceleration mode and near the end of the deceleration mode.
Further objects, features, and advantages of the present invention will become apparent from the following description of the preferred embodiments with reference to the attached drawings.